Internal development is very different than externally facing development. For example, generated API docs are a horrible thing for purely internal code, becaus

Internal development is very different than externally facing development. For example, generated API docs are a horrible thing for purely internal code, because you need a documentation build and deployment system that inevitably breaks and nobody wants to maintain and gets out of sync and suddenly the documentation is stale and there's some engineer on the brink of rage quitting if someone pings them to manually rebuild the documentation pages one more goddamn time. Having it just in the repo as a set of Markdown docs or something is much better, and "the website" is just URLs to those files in GitHub. Same risk of becoming stale as anything else, but no overhead of documentation build and deployment.